JP-A-2011-143532 discloses a replaceable cutting head, which is detachably mounted by being inserted into a mounting hole formed in a holder and by being threadedly attached to a mounting screw portion, as this replaceable head cutting tool. The replaceable cutting head includes a cutting head body and a coupling member. The cutting head body is made of a hard material, and includes a cutting edge portion that is provided at a front end portion, a mounting unit that is formed at a rear end portion and is inserted into the mounting hole, and a coupling hole that includes an inner peripheral surface on which a concave portion is formed. The coupling member is made of a metal material having hardness lower than the hardness of the hard material. The coupling member includes a front end shaft portion, a head screw portion, and a hole portion. The front end shaft portion is inserted into the coupling hole and the outer peripheral surface of the front end shaft portion comes into close contact with the inner peripheral surface of the coupling hole, so that the front end shaft portion is engaged with the coupling hole. The head screw portion is threadedly attached to the mounting screw portion. The hole portion is formed in the head screw portion and the front end shaft portion along the center line of the front end shaft portion. The coupling member is coupled to the cutting head body.
After the front end shaft portion of the coupling member is inserted into the coupling hole of the cutting head body, a punch of which an outer diameter is slightly larger than the inner diameter of the hole portion is press-fitted into the hole portion of the coupling member. Accordingly, the front end shaft portion of the coupling member is plastically deformed so as to increase in diameter, and the outer peripheral surface of the front end shaft portion penetrates into and is engaged with the concave portion of the inner peripheral surface of the coupling hole. As a result, the cutting head body and the coupling member of the replaceable cutting head are integrated with each other. Here, JP-A-2011-143532 discloses an example in which annular grooves are formed on the inner peripheral surface of the coupling hole of the cutting head body as the concave portion, and the concave portion has the shape of a substantially circular arc in a cross-section taken along the center line in FIG. 3 of JP-A-2011-143532.